I. Field of the Invention
Embodiments of this invention are directed generally to biology and medicine. In particular the invention is directed to field of gene therapy using AAVP in combination with imaging for providing therapy to a subject.
II. Background
A limitation of many biological-based therapies has been an inability to achieve controlled and effective delivery of biologically active molecules to tumor cells or their surrounding matrix. The aim of employing gene-based therapy is to achieve effective delivery of biological products, as a result of gene expression, to their site of action within the cell. Gene-based therapy can also provide control over the level, timing, and duration of action of these biologically active products by including specific promoter/activator elements in the genetic material transferred resulting in more effective therapeutic intervention. Methods are being developed for controlled gene delivery to various somatic tissues and tumors using novel formulations of DNA, and for controlling gene expression using cell specific, replication activated, and drug-controlled expression systems.
In one approach, gene therapy attempts to target cells in a specific manner. Thus, a therapeutic gene is linked in some fashion to a targeting molecule in order to deliver the gene into a target cell or tissue. Current methods typically involve linking up a targeting molecule such as a ligand or antibody that recognizes an internalizing receptor to either naked DNA or a mammalian cell virus containing the desired gene. When naked DNA is used it must be condensed in vitro into a compact geometry for entry into cells. A polycation such as polylysine is commonly used to neutralize the charge on DNA and condense it into toroid structures. This condensation process, however, is poorly understood and difficult to control, thus, making the manufacturing of homogeneous gene therapy drugs extremely challenging.
Bacteriophage (phage), such as lambda and filamentous phage, have occasionally been used in efforts to transfer DNA into mammalian cells. In general, transduction of lambda was found to be a relatively rare event and the expression of the reporter gene was weak. In an effort to enhance transduction efficiency, methods utilizing calcium phosphate or liposomes (which do not specifically target a cell surface receptor) were used in conjunction with lambda. Gene transfer has been observed via lambda phage using calcium phosphate coprecipitation, or via filamentous phage using DEAE-dextran or lipopolyamine. However, these methods of introducing DNA into mammalian cells are not practical for gene therapy applications, as the transfection efficiency tends to be low, non-specific, and transfection is not only cumbersome, but is promiscuous regarding cell type.
Currently, eukaryotic viruses unquestionably provide superior transgene delivery and transduction (Kootstra and Verma, 2003; Machida, 2003) but ligand-directed targeting of such vectors generally requires ablation of their native tropism for mammalian cell membrane receptors (Miller et al., 2003; Mizuguchi and Hayakawa, 2004; White et al., 2004). In contrast, prokaryotic viruses such as bacteriophage (phage) are generally considered poor vehicles for mammalian cell transduction. However, despite their inherent shortcomings as “eukaryotic” viruses, phage particles have no tropism for mammalian cells (Zacher et al., 1980; Barrow and Soothill, 1997; Barbas et al., 2001) and have even been adapted to transduce such cells (Ivanenkov et al., 1999; Larocca et al., 1999; Poul and Marks, 1999; Piersanti et al., 2004) albeit at low efficiency.
More reliable means of targeting vectors to specific cells (or receptors) and of guaranteeing a therapeutically useful degree of gene delivery and expression are thus required, if vectors useful in therapeutic applications are to be achieved.